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    <title>Document</title>
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    <script>
        var arr1 = [1,2,3,4];
        var arr2 = [5,[1,3,3]];
        console.log(arr1.concat(arr2[1]));
        // 可以作为克隆数组  
        var arr11 = arr1.concat([]);
    // console.log(arr1.concat([]));

    </script>
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